In an electroluminescence (EL) element, a light-emitting unit, including a light-emitting layer sandwiched by a positive electrode and a negative electrode, is formed on a transparent substrate. Upon applying a voltage between the electrodes, the EL element emits light as excitons are generated by the recombination of positive holes and electrons injected into the light-emitting layer as carriers.
EL elements are largely divided into an organic EL element, in which an organic material is used as a fluorescent material of a light-emitting layer, and an inorganic EL element, in which an inorganic material is used as a fluorescent material of a light-emitting layer. In particular, the organic EL element is capable of emitting high-brightness light at a low voltage. The organic EL element has characteristics that can obtain different emission colors depending on the kind of fluorescent materials and can be easily manufactured as a surface light-emitting body.
As an example of illumination devices using the characteristics of the EL element as a surface light-emitting body, there is known an illumination device in which sub-panels are rotatably connected to the respective sides of a rectangular organic EL panel having the same shape as the sub-panels (see, e.g., Japanese Patent Application Publication No. 2008-186599). By rotating the sub-panels, the illumination device can be transformed into a desired shape, e.g., a flat shape or a box shape. This makes it possible to improve the design merit of the illumination device.
The illumination device disclosed in JP2008-186599A includes an EL panel in which a light-emitting element (organic EL element) is accommodated within a case with the light-emitting surface thereof exposed to the outside and a connecting portion for supporting the EL panel. For this reason, the appearance of the illumination device is defined by the case and the connecting portion. Thus, the shape of the light-emitting element does not contribute to the design merit of the illumination device as a whole.